This test may be able to check for pulmonary hypertension if your pulmonary arteries or the right ventricle of your heart is enlarged. The X-ray will appear normal in about one-third of people who have pulmonary hypertension.

CT (Computed Tomography) ScanCT scanning is used during the evaluation process for pulmonary hypertension

A CT of the chest is commonly ordered while evaluating a patient for pulmonary hypertension as it is a useful tool for identifying other lung diseases that might be responsible for the patient’s symptoms.

CT scans can be performed as an outpatient at hospitals or imaging centres. There is usually little or no preparation required for a CT scan of the chest but a patient should always check with their physician or imaging centre before scheduling the test.

CT Angiogram of a patient with severe idiopathic pulmonary arterial hypertension. Note the enlarged right ventricle and the smaller left ventricle. The septum is pushed towards the left ventricle due to very high pressure inside the right ventricle

What is a CT scan?CT scans use x-rays to make detailed images of structures inside the body. The pictures are taken with the patient lying on a table with the CT scanner (a large machine with a hole in the middle) hooked to it. The part of the body being imaged will be in the hole of the scanner. The scanner rotates with each rotation taking less than a second and provides a picture of a thin slice of the area being scanned. All of these pictures are then saved together and the radiologist can view them and move through them as if he is looking directly into the body. This test can be performed with or without contrast. The contrast is an iodine dye that is used to check blood flow and look for other problems. If contrast is ordered an IV will have to be placed and the dye will be injected through the patient’s vein. There is also another variation called an HRCT or high resolution CT scan. This test is the same as a standard CT but takes more pictures of smaller slices of the area of the body being scanned. An HRCT scan can be very useful in evaluating certain types of interstitial lung diseases that may be associated with pulmonary hypertension.

What CT scan results suggest pulmonary hypertension?A radiologist will review the images and write a report, which will then be sent to the ordering physician. It is a good idea for the patient to ask for the images to be saved on a disk that they can take with them and show their physician. In most cases no results will be given to the patient at the time of the scan. The CT scan is most useful in diagnosing other lung diseases that may lead to increased pressures in the pulmonary arteries such as blood clots, tumors, or interstitial lung disease (disease in the tissue of the lung not the blood vessels). But findings such as enlarged pulmonary arteries and enlarged chambers of the right heart can be suggestive of pulmonary hypertension. The patient should have a follow up appointment to go over the results with the physician that ordered the test. It is important for the patient to fully understand what the results mean for their treatment plan. It is a good idea for pulmonary hypertension patients to keep a copy of the results for their records.

The ventilation perfusion scan or VQ scan is used to evaluate for the presence of blood clots in the lungs. VQ scanning is very important for several reasons, one being that it can help identify chronic thromboembolic pulmonary hypertension or CTEPH, a disease caused by blood clots, which is the only potentially curable form of pulmonary hypertension.

It is also important as it can identify smaller blood clots that may not be causing pulmonary hypertension but that could cause problems such as strokes down the road if not treated appropriately. Blood thinners are used to treat blood clots in the lungs otherwise known as pulmonary emboli. Certain findings are also characteristic of pulmonary hypertension.

Perfusion scan from a patient with severe chronic thromboembolic pulmonary hypertension. The right lung has nearly no blood flow. The left lung has multiple wedge shaped blood flow defects

The ventilation scan is from the same patient. The left lung has preserved ventilation. These findings are classic for CTEPH

What is a ventilation perfusion scan?The VQ or ventilation perfusion scan is usually performed in a hospital as an outpatient and involves breathing in a radioactive gas and injecting a radioactive substance into the blood via an IV. The radioactive agents are given at separate times and pictures are taken before administering the next agent. The gas fills the airways of the lungs and the substance in the blood circulates through the blood vessels of the lungs. The test then compares the blood flow traveling through the vessels of the lungs to the airflow through the airways of the lungs. Pulmonary hypertension patients usually have near normal airflow where blood flow has been compromised by diseased pulmonary vessels.

If there is normal airflow and decreased blood flow, there is a high probability of pulmonary embolisms or blood clots in the lungs.

Each patient should check in with the centre performing the test to see if there is preparation that needs to be done prior. As always, it is important to have a follow up appointment scheduled with the physician that ordered the test to go over the results. After discussing the results with the physician the patient should know if there were any indications that they may have blood clots in their lungs and if so what will the treatment plan be. Further testing such as right heart catheterisation may be ordered as the VQ scan can suggest but not officially make a diagnosis of pulmonary arterial hypertension.

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